This invention relates generally to improvements in a filter-drier unit, and more particularly to a bidirectional flow filter-drier unit for use in the liquid line of reverse-cycle refrigeration and air-conditioning systems, more commonly known as heat pumps.
There are many filter-driers in existence which have been and can be used in heat pumps, but these filter-driers are designed for refrigerant flow in one direction only so that if there is a backflow, solid contaminants that were picked up in the forward flow direction are released to the system. Consequently, the use of these existing filter-driers requires the use of two such filter-driers in the liquid line with suitable bypass valves and piping that restrict flow in one direction or requires additional liquid line piping in association with bypass valves when a single filer-drier is utilized.
Of course, an alternative to installing the existing filter-drier in the liqud line of a heat pump system, would be to install such filter-drier in the common suction line. However, such a filter-drier would have to be materially larger in size to minimize pressure drop because it would be handling vapor rather than liquid flow. In any event, many system designers prefer the filter-drier be located in the liquid line to protect the expansion valves.
These existing filter-driers cannot be back-flowed without detrimental effects, and their use requires either more than two connections, additional piping or an oversized filter-drier unit in the suction line leaving the expansion devices unprotected from contamination.